It was at this time that the cloth craft industry was established, and its prosperity would grow until the 14th century. Montivilliers sheets acquired Europe-wide fame thanks to their quality and specific colours, ranging from red to purple: the so-called “scarlets” became a luxury product. This was a time of expansion and prosperity. The foundation of the port of Le Havre de Grâce by the will of King François 1st sounded the decline of Montivilliers. The gap between the abbey and the people widened from then on.
The 16th century was also a troubled period in religious terms. The revocation of the Edict of Nantes in 1685 provoked the departure of many drapers to a more welcoming and tolerant England, actually competing with Montivilliers by producing thinner, easier-to-work sheets. The Revolution definitively abolished the abbey enclosure, which was then sold in lots. In 1792, the nuns dispersed. The abbey-church, temporarily transformed into a store, quickly resumed its function as a parish church. The infirmary was converted into a school.